Methods and apparatus for wireless communication using beamforming

Abstract

The disclosure provides a method and device for wireless communication using beamforming, the operation of the method of the wireless communication device including a plurality of antennas according to the exemplary embodiments of the disclosure includes: determining an antenna subset including at least one antenna of the plurality of antennas, transmitting a sounding reference signal (SRS) switching signal to a base station through the at least one antenna of the antenna subset, receiving a channel state information reference signal (CSI-RS) transmitted from the base station using a first beam, selecting a precoding matrix indicator (PMI) based on the CSI-RS, transmitting the selected PMI to the base station, and receiving a signal transmitted from the base station through a second beam determined based on the SRS switching signal and the PMI.

Description

[0001] This application is based on and claims priority to Korean Patent Application No. 10-2021-0003565, filed on January 11, 2021, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure generally relates to wireless communication, and more specifically, to wireless communication using beamforming techniques based on determined channel characteristics. Background Technology

[0003] Beamforming refers to a method of using multiple antennas to transmit or receive directional signals. As an example, a base station can use beamforming to transmit downlink signals to a terminal. To determine the beam to be formed, the base station can assume that the radio channels between the uplink (terminal to base station) and downlink (base station to terminal) are reciprocal, i.e., that a channel reciprocity condition exists. In this case, the base station can use beamforming to transmit the downlink signal based on the downlink channel conditions estimated from the uplink signal received from the terminal. However, due to various factors, the uplink and downlink channels may differ, which can lead to inaccurate downlink channel information, resulting in suboptimal beamforming. Summary of the Invention

[0004] This disclosure provides a wireless communication method and wireless communication apparatus for optimizing downlink beam determination of a base station by transmitting a "detection reference signal (SRS) switching signal" using techniques such as antenna selection or beam selection.

[0005] In one aspect, a method of operating a wireless communication apparatus comprising a plurality of antennas according to an exemplary embodiment of the present disclosure includes: determining an antenna subset including at least one of the plurality of antennas; transmitting an SRS handover signal to a base station via the at least one antenna of the antenna subset; receiving a Channel State Information Reference Signal (CSI-RS) transmitted from the base station via a first beam; selecting a Precoding Matrix Indicator (PMI) based on the CSI-RS; transmitting the selected PMI to the base station; and receiving a signal transmitted from the base station via a second beam determined based on the SRS handover signal and the PMI.

[0006] In another aspect, a wireless communication device according to an exemplary embodiment of the present disclosure includes: a plurality of antennas; a radio frequency integrated circuit (RFIC) including a switching network connected to the plurality of antennas, wherein the switching network is configured to transmit an SRS switching signal to a base station through at least one antenna included in a subset of antennas; and a processor configured to determine an antenna subset including at least one of the plurality of antennas, select a PMI to be provided to the base station based on CSI-RS transmitted from the base station using a first beam, and process a signal transmitted from the base station using a second beam determined based on the SRS switching signal and the PMI.

[0007] In another aspect, a method for operating a base station communicating with a wireless communication device including a plurality of antennas according to an exemplary embodiment of the present disclosure includes: receiving an SRS handover signal transmitted using a subset of antennas including at least one of the plurality of antennas; estimating uplink channel information based on the SRS handover signal; estimating downlink channel information based on the estimated uplink channel information; determining and forming a first beam based on the estimated downlink channel information; transmitting CSI-RS through the first beam; and receiving PMI from the wireless communication device. A second beam is determined and formed based on the received SRS handover signal and the received PMI, and a signal including data is transmitted through the second beam.

[0008] In another aspect, a method of operating a wireless communication device including multiple antennas includes: determining an antenna subset comprising at least two, but fewer than all, of the multiple antennas; transmitting an SRS handover signal comprising a sequence of SRSs to a base station, wherein each SRS is transmitted via a different antenna of the at least two antennas in the antenna subset; receiving a reference signal transmitted via a first beam from the base station, and selecting a PMI based on the reference signal; transmitting the selected PMI to the base station; and subsequently receiving a signal transmitted via a second beam determined based on the SRS handover signal and the PMI from the base station. Attached Figure Description

[0009] Embodiments of the inventive concept will become clearer from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1A This is a block diagram schematically illustrating a wireless communication system according to exemplary embodiments of the present disclosure, and Figure 1B It is used for explanation Figure 1A A diagram of the radio channel between a wireless communication device and a base station;

[0011] Figure 2 This is a flowchart illustrating a method of operating a wireless communication device and a base station in a wireless communication system according to exemplary embodiments of the present disclosure;

[0012] Figure 3A and Figure 3B This is a flowchart illustrating a corresponding example of a method for transmitting a probe reference signal (SRS) switching signal according to an exemplary embodiment of the present disclosure;

[0013] Figure 4 This is a flowchart illustrating an example of a method for transmitting an SRS switching signal according to a sequential antenna selection method in accordance with an exemplary embodiment of the present disclosure;

[0014] Figure 5A and Figure 5B This is a flowchart illustrating an example of a method for transmitting an SRS handover signal according to an opportunity antenna selection method in accordance with an exemplary embodiment of the present disclosure;

[0015] Figure 6 This is a flowchart illustrating an example of a method for transmitting an SRS handover signal according to an antenna spatial correlation selection method in accordance with an exemplary embodiment of the present disclosure;

[0016] Figure 7A , Figure 7B and Figure 7C This is a flowchart illustrating an example of a method for transmitting an SRS handover signal according to an antenna selection method based on reinforcement learning, according to an exemplary embodiment of the present disclosure;

[0017] Figure 8 This is a flowchart illustrating an example of a method for tracking a final subset of antennas according to an exemplary embodiment of the present disclosure;

[0018] Figure 9A and Figure 9B This is a flowchart illustrating an example of a method for selecting a precoding matrix indicator (PMI) according to an exemplary embodiment of the present disclosure; and

[0019] Figure 10A , Figure 10B and Figure 10C This is a block diagram illustrating the structure of a wireless communication device according to an exemplary embodiment of the present disclosure. Detailed Implementation

[0020] In the following, embodiments of the inventive concept will be described in detail with reference to the accompanying drawings.

[0021] Figure 1A This is a block diagram schematically illustrating a wireless communication system 10 according to an exemplary embodiment of the present disclosure, and Figure 1B It is used for explanation Figure 1A A diagram of the radio channel between the wireless communication device 100 and the base station 110.

[0022] Wireless communication system 10 can refer to any system including wireless communication device 100 and base station 110. For example, wireless communication system 10 can be any of a New Radio (NR) system, a fifth-generation wireless (5G) system, a Long Term Evolution (LTE) system, an Advanced LTE system, a Code Division Multiple Access (CDMA) system, a Global System for Mobile Communications (GSM) system, or a Wireless Local Area Network (WLAN) system. In the case of a CDMA system, this can be implemented in various CDMA versions such as Wideband CDMA (WCDMA), Time Division Synchronous CDMA (TD-SCDMA), CDMA2000, etc. In the following description, wireless communication system 10 will be primarily referred to with reference to 5G and / or LTE systems; however, it should be understood that exemplary embodiments of this disclosure are not limited thereto.

[0023] The wireless communication network of the wireless communication system 10 can support communication by multiple users by sharing available network resources. For example, in the wireless communication network, various multiple access methods (such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA, etc.) can be used to provide information.

[0024] Base station (BS) 110 may be part of wireless communication system 10. BS 110 is typically a fixed station that communicates with multiple user equipments (UEs), but in other examples, UEs may be configured to act as base stations. BS 110 may communicate with another BS 112 and may exchange data and control information by communicating with UEs and / or other “cells” (e.g., other BSs that typically serve a geographic area). For example, a BS may be referred to as a cell, Node B, Evolved Node B (eNB), Next Generation Node B (gNB), sector, site, Base Transceiver System (BTS), Access Point (AP), Relay Node, Remote Radio Header (RRH), Radio Unit (RU), small cell, etc. In this specification, the term "BS" can collectively refer to some area or function covered by the Base Station Controller (BSC) in CDMA, Node B in WCDMA, eNB in ​​LTE, gNB or sector (site) in NR, and can cover all kinds of coverage areas (such as megacells, macrocells, microcells, picocells, femtocells and relay nodes, RRH, RU and small cell communication range).

[0025] The wireless communication device 100 (hereinafter, for the sake of brevity, may be referred to as "device 100" interchangeably) may be a UE in the wireless communication system 10. "UE" may be fixed or mobile, and may refer to various devices capable of transmitting and receiving data and / or control information by communicating with the BS. For example, a UE may be referred to as a terminal device, mobile station (MS), mobile terminal (MT), user terminal (UT), user station (SS), wireless device, handheld device, etc.

[0026] like Figure 1A As shown, the wireless communication system 10 may include multiple base stations (BSs) (e.g., 110 and 112) and a system controller 120. In other examples, the wireless communication system 10 may include one or more additional cells and multiple network entities. BSs 110 and 112 may communicate with device 100 or another cell to send and receive data signals or control information. The wireless communication device 100 may communicate with the wireless communication system 10 and may also receive signals from broadcast station 114. Furthermore, the wireless communication device 100 may receive signals from satellites 130 of a Global Navigation Satellite System (GNSS). Device 100 may support radio technologies used for various wireless communications.

[0027] The technical aspects of this disclosure can be applied between communication entities forming uplink and downlink channels in wireless communication system 10. Hereinafter, apparatus 100 and BS 110 will be described as communication entities applying the technical aspects of this disclosure.

[0028] Downlink channel 102 and uplink channel 104 can form a data connection path between device 100 and BS 110. It can be assumed that the state of downlink channel 102 and the state of uplink channel 104 are the same (reciprocity condition) or similar. When the downlink and uplink channels are similar, this can be referred to as a "calibrable reciprocity condition" where calibration can be performed to effectively achieve reciprocity between the uplink and downlink channels. Thereafter, reciprocity (non-reciprocity condition) can be assumed to exist in the following description, regardless of whether calibration is performed. Reciprocity between downlink channel 102 and uplink channel 104 can exist in a time-division duplex (TDD) based wireless communication system where the uplink and downlink share the same spectrum, but uplink and downlink transmissions are separated in the time domain. In a frequency-division duplex (FDD) based wireless communication system where the uplink and downlink use different spectrums, reciprocity can also be predicted or achieved via calibration.

[0029] BS 110 can receive a sounding reference signal (SRS) transmitted by at least one of the multiple antennas included in device 100. In embodiments of this disclosure, BS 110 typically receives an SRS sequence from at least two antennas (a subset of antennas) of device 100, wherein each antenna transmits one SRS of the sequence. This SRS sequence may be referred to as an "SRS switching signal". For example, when device 100 includes multiple antennas, at least two antennas can be sequentially selected in a predetermined order, and each antenna can transmit an SRS that can be received by BS 110 and, in some cases, by the cell. BS 110 can estimate the uplink channel 104 of each antenna of device 100 and use the estimated uplink channel to estimate downlink channel information, assuming channel reciprocity.

[0030] However, even if the transmitter or receiver is calibrated to meet channel reciprocity, the channels for transmitting and receiving uplink and downlink signals may differ due to implementation issues with device 100. For example, if the number of transmit / receive antennas of the terminal differs from the number of transmit / receive RF chains, or if there are limitations on the SRS resources allocated from BS 110, then in a conventional system, BS 110 cannot obtain complete downlink channel information from the signals received by device 100.

[0031] Furthermore, when BS 110 limits SRS resources per device to support multi-user multiple-input multiple-output (MU-MIMO), device 100 is allocated limited SRS resources, for example, using fewer frequencies and / or time slots for channel measurements compared to the case of unrestricted SRS resources. When transmitting SRS in a conventional manner with limited resources, beamforming using downlink channel information obtained by BS 110 may be suboptimal.

[0032] The wireless communication system 10 according to an exemplary embodiment of the present disclosure uses the antenna or beam selection method of the apparatus 100 to efficiently transmit SRS and efficiently acquire the downlink channel, thereby obtaining beamforming-based communication with improved performance.

[0033] Further reference Figure 1B Device 100 may include m antennas 1 to m, and BS 110 may include n antennas 1 to n. Device 100 and BS 110 can use their respective antennas to perform beamforming-based communication, multiple-input multiple-output (MIMO)-based communication, etc. Because through... Figure 1B The configuration increases the theoretical channel transmission capacity, thus improving the transmission rate and significantly increasing frequency efficiency.

[0034] The uplink channel h corresponding to the j-th antenna of the wireless communication device 100 j (1≤j≤m, j is an integer) can include channels h corresponding to the corresponding n antennas of BS 110. 1,j h 2,j , ..., h n,j BS 110 can receive the SRS transmitted from the j-th antenna of device 100 and use the received SRS to estimate the uplink channel h. j BS 110 can, under the assumption of channel reciprocity, determine the uplink channel h. j The downlink channel is estimated, the estimated downlink channel is used to generate a downlink signal, and the downlink signal is transmitted to the device 100 through at least one of the n antennas.

[0035] The uplink channel h corresponding to the j-th antenna of device 100 can be... j The description applies to the uplink channel corresponding to other antennas of device 100, and based on the above, the technical concept of this disclosure will be described below.

[0036] Note that the terms "antenna selection" and "beam selection" are used interchangeably throughout this specification. The following description will primarily use the term "antenna selection" to describe some of the technical concepts of this disclosure.

[0037] Figure 2 This is a flowchart illustrating a method of operating device 100 and BS 110 in a wireless communication system according to an exemplary embodiment of the present disclosure. In this method, the wireless communication system 10 may include device 100 and BS 110, and in operation S210, device 100 may send an “SRS handover signal” to BS 110 using SRS handover resources set by BS 110 (device 100 may have already learned of the SRS handover resources in pilot signal exchange with the BS). As previously described, the SRS handover signal includes a plurality of SRSs transmitted sequentially, wherein each SRS is transmitted from a corresponding antenna in the antennas of device 100. The “SRS handover resource” can be defined as a set of uplink resource elements (REs) (e.g., a set of frequencies and / or time slots used for SRS transmission) used when device 100 transmits the SRS signal to obtain channel information for downlink beamforming by BS 110. BS 110 may allocate SRS handover resources to device 100.

[0038] According to one embodiment, the available resources of BS 110 are limited to the transmission of SRS handover signals. In this case, the SRS handover resources allocated by BS 110 for SRS handover signals are less than the number of receiving antennas of device 100. In this case, only some antennas are used for transmission (“first scenario”). For example, assuming there are 5 wireless communication devices in a cell covered by BS 110 and each wireless communication device 100 includes 4 antennas, if there are 16 resources that can be allocated by BS 110, some of the 5 wireless communication devices cannot be allocated 4 SRS handover resources (assuming that the handover resources are to be used simultaneously).

[0039] In another scenario, due to limitations in the hardware implementation of the wireless communication device 100 when transmitting SRS switching signals, there may be a situation where only some antennas are used for transmission (“Second Scenario”). This corresponds to the case where the number of Tx radio frequency (RF) chains in device 100 is less than the number of receiving antennas 100. For example, due to limitations in the hardware implementation of device 100, the number of receiving antennas may be four, but the number of transmitting antennas may be limited to two.

[0040] In the following discussion, to facilitate understanding of the concepts taught herein, an example of device 100 having four receiving antennas is given. In other examples, these concepts are applied to device 100 with more or fewer antennas.

[0041] The following will refer to further details. Figure 3A and Figure 3B Describe the antenna selection and antenna switching operations.

[0042] In operation S220, BS 110 can estimate uplink channel information based on the received SRS handover signal. In operation S230, BS 110 can estimate downlink channel information by performing operations such as calibration based on the estimated uplink channel information. Here, calibration refers to a series of processes (e.g., passing through RF filters from the baseband at transmission to the baseband at reception) to ensure reciprocity of the uplink and downlink channels throughout the signal path. In operation S240, BS 110 can use the estimated downlink channel information to determine beamforming, and in operation S250, beamforming is used to transmit a Channel State Information Reference Signal (CSI-RS). Depending on which antenna(s) are selected, the CSI-RS transmitted by BS 110 to device 100 may include different information.

[0043] In operation S260, device 100 may select a precoding matrix indicator (PMI) based on the received CSI-RS, and in operation S270, the selected PMI is sent to BS 110. When selecting a PMI, device 100 may take into account information about the selected antenna, and thus may select the optimal PMI.

[0044] In operation S280, BS 110 can use information obtained from the SRS handover signal received in operation S210 and information obtained from the PMI received in operation S270 to determine the final downlink beamforming, and in operation S290, transmit downlink signals including data through the antenna beam determined by the beamforming.

[0045] The beam determined in operation S280 may be referred to as the “final beam” below, and may be defined in the form of a matrix as follows.

[0046] [Equation 1]

[0047] x = F SRS F PMI S

[0048] F SRS (Number of antennas in BS 110 × Number of CSI-RS antenna ports) can be defined as a matrix of beams based on the SRS switching signals received from device 100, and F PMI (Number of CSI-RS antenna ports × Number of data layers or data streams) can be defined as a matrix based on the beams of the PMI received from device 100. s (Number of data layers or data streams × 1) can be defined as a matrix including the downlink signals of the data that BS 110 wants to transmit to device 100.

[0049] BS 110 can use all the information obtained from the SRS switching signal and PMI to form the final synthesized beam, and can perform beamforming with device 100. SRS and F PMI It can be represented as the matrix F of the final synthesized beam. SRS_PMI (That is, in the form of a beam). x (number of BS antennas × 1) corresponds to the final signal transmitted from BS 110 to device 100.

[0050] According to the above operating method, the device 100 adaptively transmits the SRS switching signal and adaptively transmits the PMI to optimize the acquisition of downlink channel information and the beamforming decision of the BS 110.

[0051] Additionally, refer to Figure 2The CSI-RS corresponding to the downlink reference signal and the SRS corresponding to the uplink reference signal described are merely examples of reference signals that can be applied in this method. Optional reference signals may include pilot signals for channel estimation transmitted by the BS in the downlink and pilot signals for channel estimation transmitted by the wireless communication device in the uplink.

[0052] Figure 3A and Figure 3B This is a flowchart illustrating an example of a method for transmitting an SRS switching signal according to an exemplary embodiment of the present disclosure.

[0053] Figure 3A It shows in Figure 2 The process of determining an antenna subset in operation S210 to select the antenna for transmitting the SRS switching signal.

[0054] In operation S310a, BS 110a can transmit a downlink reference signal to wireless communication device 100a (hereinafter referred to as "device 100a"). In operation S320a, device 100a can estimate downlink channel information from the received CSI-RS, and in operation S330a, determine an antenna subset based on the estimated downlink channel information. The antenna subset can be determined based on at least one of the signal-to-interference-plus-noise ratio (SINR) of the wireless communication device, the transmit / receive characteristics of the antenna, and the linearity of the transmit power amplifier. In operation S340a, device 100a can transmit an SRS handover signal by including at least one of the antennas in the determined antenna subset.

[0055] In an exemplary embodiment, the method for determining an antenna subset may include: a method for sequentially determining an antenna subset and then switching the antenna subset according to the transmission period of the SRS switching signal; a method for non-periodicly switching the antenna subset after determining the antenna subset based on the gain value / signal quality metric of a specific beam; a method for switching the antenna subset after determining the antenna subset based on the spatial correlation between the receiving antennas of the wireless communication device; and a method for switching the antenna subset according to an update period after determining the antenna subset based on reinforcement learning. (Refer to below) Figure 4 Provide a detailed description of this.

[0056] Reference Figure 3B , showing in Figure 2 The process of selecting a beam to send an SRS switching signal in operation S210.

[0057] In operation S310b, BS 110b can transmit a downlink reference signal to wireless communication device 100b (“device 100b”). In operation S320b, device 100b can estimate downlink channel information from the received CSI-RS, and in operation S330b, determine the beams for transmitting SRS handover signals from each antenna based on the estimated downlink channel information. For example, device 100b can select beams with good reception performance and spatial characteristics from a previously designed beamcodebook using the estimated downlink channel information, or it can redesign the beams if no pre-designed beamcodebook is available. In operation S340b, the determined beams can be used to transmit the SRS handover signals.

[0058] Table 1 below shows the beam codebook according to embodiments of the present disclosure.

[0059] [Table 1]

[0060] Antenna #1 A11+B11i A12+B12i A13+B13i A14+B14i Antenna #2 A21+B21i A22+B22i A23+B23i A24+B24i Antenna #3 A31+B31i A32+B32i A33+B33i A34+B34i Antenna #4 A41+B41i A42+B42i B43+B43i A44+B44i

[0061] Referring to Table 1, in this example, it is assumed that there are four antennas of device 100b and four beams can be formed from each antenna. For example, the beam codebook includes indices of a pre-coded matrix shared in device 100b and BS 110b. The elements of each antenna used for beam configuration can be represented as arbitrary complex values. For example, the real part of the second beam of antenna #4 is A42, and the imaginary part is B42.

[0062] Table 2 below shows the beam codebook according to embodiments of the present disclosure.

[0063] [Table 2]

[0064] Antenna #1 1 1 1 1 Antenna #2 1 -1i -1 1i Antenna #3 1 -1 1 -1 Antenna #4 1 1i -1 -1i

[0065] Referring to Table 2, among the elements used to configure the third antenna, the elements for the third beam can consist of 1.

[0066] Figure 4 This is a flowchart illustrating an example of a method for transmitting an SRS switching signal according to a sequential antenna selection method in accordance with an exemplary embodiment of the present disclosure.

[0067] Figure 4 The example illustrates a method for transmitting SRS switching signals by sequentially determining antenna subsets and then switching the antenna subsets according to the SRS transmission period. This can be referred to as the "sequential antenna selection method".

[0068] exist Figure 4In this context, it is assumed that the number of receiving antennas in device 100 is 4, and that the SRS handover signal is transmitted to BS 110 using two transmitting antennas, which is less than the number of receiving antennas. That is, it is assumed that the size of the antenna subset determined by device 100 is 2. For example, this corresponds to when BS 110 allocates two SRS handover resources to device 100 (first scenario) or when only two antennas are used due to hardware implementation limitations of device 100.

[0069] In an embodiment, when the indices of the first antenna, the second antenna, the third antenna, and the fourth antenna are {0, 1, 2, 3} respectively, a subset of the combination of two antennas from the first antenna to the fourth antenna for transmitting SRS switching signals can be configured as follows.

[0070] Antenna subsets: {0, 1}, {0, 2}, {0, 3}, {1, 2}, {1, 3}, {2, 3}

[0071] In an exemplary embodiment, the device 100 may sequentially determine each of the six possible antenna subsets in a predefined order.

[0072] Here, the fact that the antenna subsets are determined sequentially means, for example, selecting six possible antenna subsets in {0,1}, {0,2}, {0,3}, {1,2}, {1,3}, and {2,3} for each transmission cycle of the SRS switching signal.

[0073] For example, in operation S402, the device 100 may determine the subset of antennas transmitting the SRS handover signal as {0, 1} during the first SRS handover transmission cycle. That is, the device 100 may determine to transmit the SRS handover signal using the first antenna and the second antenna out of the four antennas. In some embodiments, the device 100 may determine each of the antenna subsets in a different order than described above.

[0074] In operation S404, after transmitting SRS_0 as an SRS handover signal using the first antenna and SRS_1 as an SRS handover signal using the second antenna, in operation S406, BS 110 can use SRS_0 and SRS_1 to design the downlink beam F_SRS. In operation S408, BS 110 can transmit CSI-RS through the F_SRS beam.

[0075] In operation S410, device 100 can select PMI based on the received CSI-RS, and in operation S412, the PMI is fed back to BS 110. In operation S414, BS 110 can use the received PMI to design the downlink beam F_PMI, and in operation S416, the downlink signal including data is transmitted to device 100 using the final beam determined by F_SRS and F_PMI.

[0076] As an exemplary embodiment, operations S402 to S416 can be performed by device 100 within a time period corresponding to the first SRS switching signal transmission period, and can be referred to as period 1. In the second SRS switching signal transmission period corresponding to period 2, it is determined that antenna subset {0, 2} transmits SRS switching signals, and for example, in period 4 corresponding to the fourth SRS switching signal transmission period, it is determined that antenna subset {1, 2} transmits SRS_1 and SRS_2 to BS 110.

[0077] In operation S418, after repeating a number of SRS handover transmission cycles, the device 100 may determine the subset of antennas used to transmit the SRS handover signal as {1, 2} in the fourth SRS handover transmission cycle. That is, the device 100 may determine the transmission of the SRS handover signal by using the second and third antennas out of the four antennas. In some embodiments, the device 100 may determine each antenna in the subset in an order different from the order described above.

[0078] In operation S420, after transmitting SRS_0 as an SRS handover signal using the first antenna and SRS_1 as an SRS handover signal using the second antenna, in operation S422, BS 110 can use SRS_0 and SRS_1 to design the downlink beam F_SRS. In operation S424, BS 110 can transmit CSI-RS through the F_SRS beam.

[0079] In operation S426, device 100 can select PMI based on the received CSI-RS, and in operation S428, the PMI is fed back to BS 110. In operation S430, BS 110 can use the received PMI to design the downlink beam F_PMI, and in operation S432, the downlink signal including data is transmitted to wireless communication device 100 using the final beam determined by F_SRS and F_PMI.

[0080] according to Figure 4The method shown allows device 100 to monitor the "gain" of the final beam during each SRS switching signal transmission cycle and sequentially consider all possible subsets of antennas to find the optimal antenna combination. Here, "beam gain," or simply "gain" or "gain value," can be defined as a term related to the signal quality of the signal transmitted from the base station and received by the antenna beam of the wireless communication device (e.g., 100) (since the distance between BS 110 and device 100 is typically unknown). In the following text, the terms "gain" and "signal quality" can be used interchangeably. Gain can be determined by the power of the signal received by device 100, the signal-to-noise ratio (SNR) of the signal received by device 100, the signal-to-interference-plus-noise ratio (SINR) of the signal received by device 100, frequency efficiency, and / or decoding performance of the received signal.

[0081] According to embodiments of this disclosure, the subset of antennas ultimately selected as the optimal antenna combination may be referred to as the "final antenna subset".

[0082] Note that in the example above, the antenna subset size of 2 is a concept used to help understand the teachings of this article. In other examples, more or fewer antennas can form an antenna subset.

[0083] Figure 5A and Figure 5B This is a flowchart illustrating an example of a method for transmitting an SRS switching signal according to an opportunistic antenna selection method in accordance with an exemplary embodiment of the present disclosure.

[0084] Figure 5A This paper illustrates a method for transmitting an SRS switching signal based on the aperiodic switching of an antenna subset after determining the antenna subset according to the gain value of a specific beam. This can be referred to as one of the "opportunistic antenna selection methods".

[0085] In the opportunistic antenna selection method, a specific value corresponding to the beam gain is preset as a threshold B. th Furthermore, when the gain value of the final beam determined to be an arbitrary antenna subset is less than a threshold, different antenna subsets can be immediately determined regardless of the order. When the gain value of the final beam determined to be an arbitrary antenna subset is greater than the threshold, the processing for determining another antenna subset and sending the SRS switching signal can be stopped, and the corresponding antenna subset can be declared as the optimal antenna combination. In other words, the corresponding antenna subset can be determined as the "final antenna subset".

[0086] Furthermore, after determining the final antenna subset, device 100 can track the optimal antenna combination using any tracking period. There may be methods to change an antenna included in the previously determined final antenna subset, and there may be methods to change one or more antennas. When the gain of the final beam decreases rapidly, antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced with another antenna subset. Tracking and the tracking period can be determined based on indicators related to changes in the radio channel.

[0087] Specifically, refer to Figure 5A In operation S510a, device 100 can determine any subset of antennas used to transmit SRS switching signals, and after operation S510a, it can execute reference... Figure 2 Operations S210 to S290 are described, and their details will be omitted.

[0088] As an exemplary embodiment, in operation S520a, device 100 can monitor the gain value of the final beam received in operation S290. In operation S530a, device 100 can determine whether the monitored gain value of the final beam exceeds a threshold B. th .

[0089] In operation S540a, when the gain value of the final beam monitored by device 100 exceeds threshold B th At that time, the antenna subset determined in operation S510a can be determined as the final antenna subset.

[0090] On the other hand, when the gain value of the final beam monitored by device 100 is less than or equal to threshold B th When the process returns to operation S510a to determine the antenna subset, device 100 may return to operation S510a, select antenna subset {2, 3}, and transmit SRS switching signals using the third and fourth antennas.

[0091] Figure 5B This paper illustrates a method for transmitting an SRS switching signal based on an aperiodic switching method of the antenna subset after determining the antenna subset according to the channel gain values ​​corresponding to all antennas used for receiving CSI-RS. This can be referred to as one of the "opportunistic antenna selection methods".

[0092] In an embodiment, when the channel gains corresponding to all antennas used to receive CSI-RS have similar values, the apparatus 100 may determine the antenna subset identified in an operation similar to S510b as the final antenna subset. According to embodiments, the criteria for whether the channel gains have similar values ​​may be set differently.

[0093] On the other hand, when there is a relatively large difference in channel gain corresponding to all antennas used to receive CSI-RS, the device 100 can return to the operation of determining a subset of antennas similar to S510b and continuously try to send SRS switching signals using a new subset of antennas.

[0094] In operation S510b, device 100 can determine any subset of antennas used to transmit the SRS switching signal, and after operation S510b, it can execute the reference... Figure 2 Operations S210 to S290 are described (detailed descriptions omitted here).

[0095] As an exemplary embodiment, in operation S520b, device 100 can monitor the gain value of the channel receiving CSI-RS in operation S290. In operation S530b, device 100 can determine whether the absolute value of the difference between the monitored channel gain values ​​exceeds a threshold C. th .

[0096] When the absolute value of the difference between the channel gain values ​​monitored in operation S520b exceeds the threshold C th In operation S540b, device 100 may determine the final antenna subset as the antenna subset determined in operation S510b.

[0097] On the other hand, when the absolute value of the difference between the channel gain values ​​monitored by device 100 is less than or equal to threshold C th When the process returns to operation S510b to determine the antenna subset, device 100 may return to operation S510b, select antenna subset {2, 3}, and thereafter periodically or continuously transmit SRS switching signals using the third and fourth antennas.

[0098] Furthermore, after determining the final antenna subset, device 100 can track the optimal antenna combination using any tracking period. This can be achieved by changing one antenna included in the previously determined final antenna subset, or by changing one or more antennas. During tracking, if the gain of the final beam decreases rapidly, antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced with another antenna subset. Tracking and the tracking period can be determined based on indicators associated with changes in the radio channel.

[0099] Figure 6 This is a flowchart illustrating an example of a method for transmitting an SRS handover signal according to an antenna spatial correlation selection method in accordance with an exemplary embodiment of the present disclosure.

[0100] Specifically, Figure 6A method for transmitting an SRS handover signal according to a method for switching antenna subsets (“Method 3”) is illustrated after determining an antenna subset based on the spatial correlation between the receiving antennas of the wireless communication device. Method 3 may be referred to as the “selection method based on antenna spatial correlation”.

[0101] Spatial correlation between antennas can be defined as an index indicating the degree of interference between antennas, determined by factors such as the distance between them. For example, when spatial correlation between antennas is low, different signals can be transmitted independently by the antennas. Therefore, according to embodiments of this disclosure, low spatial correlation between antennas is desired for a subset of antennas used for SRS switching signals. Methods considering spatial correlation between antennas can have the purpose of transmitting signals via antennas that guarantee relatively independent channels by selecting combinations of antennas based on channel information.

[0102] The spatial correlation between antennas can be determined by frequency band, BS coverage cell type, antenna spacing, polarization, etc.

[0103] According to an embodiment, the antenna subsets can be arranged in order of lowest to highest spatial correlation among the receiving antennas of the device 100, and then sequentially determined as the antenna subsets for transmitting SRS switching signals.

[0104] Optionally, the antenna subsets can be arranged in order of the highest to lowest spatial correlation among the receiving antennas of the device 100, and then sequentially determined as the antenna subsets for transmitting SRS switching signals.

[0105] In another embodiment, the arrangement of multiple antennas of device 100 can be considered to switch antenna subsets without measuring spatial correlation. For example, antenna subsets can be arranged in the following order based on the antenna combination with the largest antenna spacing distance value.

[0106] Antenna subsets: {0, 3}, {0, 2}, {1, 3}, {0, 1}, {1, 2}, {2, 3}

[0107] Reference Figure 6 In operation S610, device 100 can arrange antenna subsets in order of lowest to highest correlation between antennas. In operation S620, one of the antenna subsets listed in operation S610 is sequentially selected and determined as the i-th antenna subset. After operation S620, reference can be executed. Figure 2 Operations S210 to S290 are described (their redundant descriptions are omitted).

[0108] In operation S630, device 100 monitors the gain value of the final beam. For example, assuming that the number of antennas included in device 100 is 4 and the antenna subset is a combination of two antennas, there are a total of six possible antenna subsets, and operations S620 to S630 are repeated a total of six times.

[0109] In operation S640, when the final beam gain value of all antenna subsets has been monitored, in operation S650, the antenna subset with the maximum gain value can be determined as the final antenna subset.

[0110] Furthermore, after determining the final antenna subset, device 100 can track the optimal antenna combination using any tracking period. This can be achieved by changing one antenna included in the previously determined final antenna subset, or by changing one or more antennas. During tracking, if the gain of the final beam decreases rapidly, antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced with another antenna subset. Tracking and the tracking period can be determined based on indicators associated with changes in the radio channel.

[0111] Furthermore, according to one embodiment, if an SRS handover resource is allocated by BS 110 for the SRS handover signal according to the "first scenario" (mentioned above), then after determining the antenna subset based on the antenna's receiving performance, the device 100 can switch the antenna subset to transmit the SRS handover signal. For example, the antenna subset can be determined sequentially after arranging antennas with high antenna receiving power in ascending order or antennas with low antenna receiving power in ascending order.

[0112] Figures 7A to 7C This is a flowchart illustrating an example of a method for transmitting an SRS switching signal according to an antenna selection method based on reinforcement learning, in accordance with an exemplary embodiment of the present disclosure.

[0113] Reference Figures 7A to 7C After determining the antenna subset based on reinforcement learning by switching antenna subsets according to the update cycle, an SRS switching signal can be sent. This can be called a "reinforcement learning-based antenna selection method".

[0114] Reinforcement learning is a type of machine learning and can be defined as a method in which an agent, defined in a specific environment, identifies its current state and selects an action or sequence of actions from a pool of available actions that maximizes the reward. Reinforcement learning can be performed by the machine learning device 1010c of device 100, and will be discussed later. Figure 10C Describe the operation of the machine learning device 1010c.

[0115] According to embodiments of this disclosure, the antenna selection method based on reinforcement learning includes an antenna selection method based on Q-learning and an antenna selection method based on Bandit learning.

[0116] Figure 7A This is a flowchart illustrating a method for transmitting SRS switching signals according to a Q-learning-based antenna selection method during reinforcement learning.

[0117] A Q-function, denoted as "(state, action)" (which is a pair of states and actions), can be defined as a function that can predict the expected value of the utility provided by performing a given action in a given state. According to an embodiment, device 100 may select an antenna combination with a large Q-value (i.e., Q(S, A)).

[0118] In an embodiment, an action can be defined as the action of selecting an antenna combination for determining an antenna subset, and a state (representing the state when a particular antenna is selected) can be defined as a parameter related to the downlink channel. The parameters related to the downlink channel can be determined by correlation in the time, spatial, and frequency domains, as well as the strength of the downlink signal. The reward can be defined as a reception performance index of the downlink signal including data received from device 100, either from CSI-RS or using the final beam. The reception performance of the downlink signal can be determined by the block error rate (BLER), frequency efficiency, and strength of the downlink signal.

[0119] Table 3 shows the Q table according to an embodiment of the present disclosure.

[0120] [Table 3]

[0121] S_1 Q(S_1,A_1) Q(S_1,A_2) … Q(S_1,A_N) … … … … … S_M Q(S_M,A_1) Q(S_M,A_2) … Q(S_M,A_N)

[0122] Referring to Table 3, for example, A_1 may represent the case where the antenna subset determined by device 100 is {0, 1}. S_1 may represent the state corresponding to one of the downlink-related parameter values, which has up to M possible values ​​due to various factors (such as correlation in the time domain, spatial domain, frequency domain, and the strength of the downlink signal).

[0123] Q(S_M, A_N) takes the action of selecting a subset of antennas including the Nth antenna combination, and can represent the Q value in the case of a state corresponding to a parameter numbered M based on the antenna combination.

[0124] In an exemplary embodiment, the update operation of Q can be represented as follows.

[0125] [Equation 2]

[0126]

[0127] α can be defined as the learning rate factor, and can have a value greater than 0 and less than or equal to 1. R corresponds to the reward value, and γ is the discount factor, which can be defined as a value indicating how important the current reward is compared to the reward to be obtained in the future. Q(S′, A) can be defined as the expected optimal Q value in the future state S′.

[0128] Specifically, in operation S710a, which is the first operation of the Q-based learning algorithm, the device 100 can initialize Q(S, A) to arbitrary values. After initializing Q, the following process is repeated for each segment:

[0129] In operation S720a, device 100 selects whether to take an action randomly with probability e, or whether to take an action satisfying probability (1-e). The action. In operation S730a, device 100 observes the reward and new state value S′ based on the selected action, and updates the Q value using [Equation 2] in operation S740a (i.e., calculates Q). new (S, A)). In operation 750a, device 100 determines whether the segment has ended, and if device 100 determines that the segment has not ended, then in operation S760a, S′ is updated to S.

[0130] According to an embodiment, the device 100 can select an antenna combination constituting an antenna subset based on Q, and after determining the antenna subset, calculate the state and reward and update Q to determine another antenna subset based on the updated Q.

[0131] Figure 7B This is a flowchart illustrating a method for transmitting SRS switching signals during reinforcement learning based on an antenna selection method using an upper confidence interval (UCB) algorithm.

[0132] The UCB algorithm can be defined as an algorithm that finds an upper bound (i.e., the UCB value) with a high probability of yielding the expected reward at a specific time t based on observations during the time period. For example, the UCB is updated for each action that selects an antenna combination that includes an antenna combination in a subset of antennas, and device 100 can select an antenna subset that includes antenna combinations with large UCBs. This can be referred to as one of the "bandit-based antenna selection methods".

[0133] In an exemplary embodiment, the UCB value can be represented as follows.

[0134] [Equation 3]

[0135]

[0136] In an exemplary embodiment, the reward and the average experience of the reward can be represented as follows.

[0137] [Equation 4]

[0138] Here T k (t+1)=T k (t)+1

[0139] T k (t) can be defined as the number of times the corresponding antenna subset is selected up to time t, and δ can be defined as the learning parameter. Additionally, X k (t) can be defined as the reward observed at the k-th action at time t. Additionally, It can be defined as the average experience of accumulated rewards up to time t.

[0140] For example, in operation S710b, device 100 can calculate the UCB at time t, and in operation S720b, it can select the antenna combination that maximizes the calculated UCB. Additionally, in operation S730b, device 100 can measure the CSI-RS channel by selecting one of the chosen antenna combinations. In operation S740b, device 100 can use [Equation 4] to calculate the reward and the empirical mean of the reward.

[0141] The UCB algorithm can operate from S710b to S740b, and can repeat S710b to S740b any number of times.

[0142] Figure 7C This is a flowchart illustrating a method for transmitting SRS switching signals according to a probability distribution-based antenna selection method during reinforcement learning.

[0143] As one embodiment, device 100 can determine a subset of antennas by using values ​​that represent the preference for selecting antenna combinations as probabilities. This can be referred to as one of the "bandit learning-based antenna selection methods".

[0144] The initial probability of preference can be arbitrarily set to Where K can be defined as the number of antenna combinations (i.e., the number of all possible antenna subsets). In operation S710c, device 100 can determine the antenna subset including the selected antenna combinations based on the learned probability distribution.

[0145] In operation of S720c, device 100 can set a positive or negative reward based on an index indicating the performance of the CSI-RS channel assigned to the selected antenna combination. For example, an index indicating the performance of a CSI-RS channel may include the signal-to-interference-plus-noise ratio (SINR).

[0146] In an exemplary embodiment, the reward can be calculated as follows.

[0147] [Equation 5]

[0148]

[0149] In operation of S720c, device 100 can use [Equation 5] to calculate the reward based on the performance of the CSI-RS channel.

[0150] Alternatively, in operation S730c, device 100 can update the reward for antenna combinations with high correlation by introducing weights w. For example, the reward can be updated by multiplying the (k-1)th reward and the (k+1)th reward by weights w1 and w2, respectively (e.g.: Next, in operation S740c, device 100 updates the probability distribution value by accumulating rewards over a predetermined time. α can be the weight of positive rewards, and β can be the weight of negative rewards.

[0151] As an exemplary embodiment, the probability distribution of cumulative rewards can be represented as follows.

[0152] [Equation 6]

[0153]

[0154] The probability distribution-based antenna selection method can be operated from S710c to S740c, and can be repeated from S710c to S740c any number of times.

[0155] As an exemplary embodiment, the probability of preference can be updated as follows.

[0156] [Equation 7]

[0157]

[0158] In the aforementioned reinforcement learning-based antenna selection schemes, actions can be applied by extending the selection of antenna combinations for determining antenna subsets and the selection of transmit power. For example, the actions can be defined as follows.

[0159] Action_i: Select the first antenna and the third antenna & set the transmit power of the first antenna to P_level4 and the transmit power of the third antenna to P_level2.

[0160] Action_j: Select antenna 0 and antenna 3 & set the transmit power of antenna 0 to P_level1 and the transmit power of antenna 3 to P_level2.

[0161] For example, P_level2 can represent the power corresponding to level2 set by device 100.

[0162] Figure 8 This is a flowchart illustrating an example of a method for tracking a final subset of antennas according to an exemplary embodiment of this disclosure.

[0163] Reference Figure 8 This shows the effect of referring to Figures 4 to 7C The described method is a method for tracking the determined final subset of antennas.

[0164] pass Figures 4 to 7C In one embodiment, during operation S810, device 100 can determine a final subset of antennas configured with the optimal antenna combination. After determining the final antenna subset, during operation S820, device 100 can track the optimal antenna combination at any tracking period, and during operation S830, it can change one or more antennas included in the previously determined final antenna subset based on the tracking results.

[0165] As an example, when the gain of the final beam decreases rapidly, antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced with another antenna subset. For example, if the antenna subset size is 3, the antenna may be changed to 1, 2, or a different antenna subset with an antenna subset size of 3. Tracking and the tracking period are determined from indicators related to changes in the radio channel, and the tracking period may be a value that corresponds to a multiple of the transmission period of the SRS handover signal. For example, the tracking period may be determined based on Doppler characteristics, which are indices of the time variation of the radio channel, and the tracking period may be set shorter when the Doppler transition value of the wireless communication device is large and longer when the Doppler transition value is small.

[0166] Figure 9A and Figure 9B This is a flowchart illustrating an example of a method for selecting a precoding matrix indicator (PMI) according to an exemplary embodiment of the present disclosure.

[0167] When devices 100a and 100b transmit SRS using limited SRS resources and antennas due to the constraints of scenarios 1 and 2 described above, beamforming using downlink channel information obtained from the BS results in loss. Therefore, methods for selecting the PMI to minimize signal loss using downlink beamforming received by devices 100a and 100b can include PMI selection methods based on channel application weights, reinforcement learning-based PMI selection methods, etc.

[0168] Figure 9A This is a flowchart illustrating a method for selecting a weighted PMI according to an exemplary embodiment of the present disclosure.

[0169] Reference Figure 9A An example of a PMI selection method is shown, which minimizes redundancy of information received by device 100a and minimizes signal loss using beamforming. Specifically, the PMI can be selected by applying different weights to the channels corresponding to antennas used to transmit SRS handover signals and antennas not used to transmit SRS handover signals.

[0170] For example, in operation S902a, device 100a can determine the subset of antennas transmitting the SRS handover signal as {0, 1} during the first SRS handover transmission cycle. In operation S904a, after transmitting SRS_0 as the SRS handover signal using the first antenna and SRS_1 as the SRS handover signal using the second antenna, in operation S906a, BS 110a can use SRS_0 and SRS_1 to design the downlink beam F_SRS. In operation S908a, BS 110a can transmit CSI-RS through the F_SRS beam. Assuming the channels used for CSI-RS reception are h0, h1, h2, and h3, in operation S910a, device 100a can set the weights applied to each channel as w0, w1, w2, and w3. w0 to w3 can be determined based on the selection and use when transmitting the SRS handover signal. For example, the weights w0 and w1 of the first and second antennas used to transmit SRS handover signals, and the weights w2 and w3 of the third and fourth antennas not used to transmit SRS handover signals, can be set differently. In operation S912a, device 100a can use the information obtained by applying weights to each channel [w0×h0, w1×h1, w2×h2, w3×h3] to select the PMI, and in operation S914a, the selected PMI is fed back to BS 110a.

[0171] According to an embodiment, the weight can be set to a larger value as the gain of the channel corresponding to the antenna decreases. Optionally, the weights can be set such that the gains of the channels corresponding to the weighted antennas are all the same.

[0172] Figure 9B This is a flowchart illustrating a reinforcement learning-based method for selecting a PMI according to an exemplary embodiment of the present disclosure.

[0173] Reference Figure 9B For example, in the antenna combination selection method, a method for selecting PMI based on reinforcement learning is shown.

[0174] According to an embodiment, in operation S902b, device 100b can determine the subset of antennas transmitting the SRS handover signal during the first SRS handover transmission period as {0, 1}. In operation S904b, after transmitting SRS_0 as the SRS handover signal using the first antenna and SRS_1 as the SRS handover signal using the second antenna, in operation S906b, BS 110b can use SRS_0 and SRS_1 to design the downlink beam F_SRS. In operation S908b, BS 110b can transmit CSI-RS through the F_SRS beam. In operation S912b, device 100 can use reinforcement learning to select the PMI. Specifically, PMI selection methods based on UCB in Q-learning and bandit learning, as well as gradient-based bandit learning in bandit learning, can be applied. As an example, the action can be defined as the action of selecting the PMI, the state can be defined as the performance index of the channel receiving the CSI-RS signal, and the reward can be defined as the performance index of the channel receiving the downlink signal using the final beam. In other words, device 100b can select the PMI that maximizes the "performance of the final beam receiving channel" corresponding to the reward from the selectable PMIs by identifying the state representing the performance of the channel used to receive CSI-RS signals. In operation S914b, wireless communication device 100b can feed back the selected PMI to BS 110b.

[0175] Figures 10A to 10C This is a block diagram illustrating the structure of a wireless communication device according to an exemplary embodiment of the present disclosure.

[0176] Figure 10A This is a block diagram illustrating the structure of a wireless communication device based on an antenna selection method according to an exemplary embodiment of the present disclosure.

[0177] Reference Figure 10A The device 100a may include a first antenna to the m-th antennas 1 to m, a radio frequency integrated circuit (RFIC) 1002a, and a processor 1006a. RFIC 1002a may include a switching network 1004a and a first RF chain to the n-th RF chain. RFIC 1002a may include multiple RF chains, and the device 100a may include multiple RFICs. The switching network 1004a may be connected to the first antenna to the m-th antennas 1 to m. In some cases, only one RF chain may be in RFIC 1002a, or it may be connected to each individual antenna.

[0178] According to an exemplary embodiment of the present disclosure, processor 1006a can identify downlink reference signals from SRS handover resources set by BS 110a. Processor 1006a can use the downlink reference signals to generate downlink channel information, select an antenna combination including at least one antenna from the first antenna to the m-th antenna, determine an antenna subset including the corresponding antenna combination, and control the switching network 1004a based on the determined antenna subset.

[0179] The switching network 1004a according to an exemplary embodiment of the present disclosure can be connected to the processor 1006a. Furthermore, the switching network 1004a can select at least one of the antennas included in an antenna subset determined by the processor 1006a. An SRS switching signal can be transmitted to the BS 110a via the selected antenna.

[0180] According to an embodiment of this disclosure, processor 1006a can select a PMI based on CSI-RS received from BS 110a using a first beam, and can send the selected PMI to the BS. BS 110a can use the final beam to transmit downlink signals including data, and processor 1006a can process the received downlink signals. The final beam can be determined using information obtained from the SRS switching signal and information obtained from the PMI.

[0181] Figure 10B This is a block diagram illustrating the structure of a wireless communication device based on a beam selection method according to an exemplary embodiment of the present disclosure.

[0182] Reference Figure 10B The device 100b may include first antennas 1 to m, RFIC 1002b, and processor 1006b. RFIC 1002b may include beamformer 1004b and first to nth RF chains. RFIC 1002b may include multiple RF chains, and the device 100b may include multiple RFICs. Beamformer 1004b may be connected to first antennas 1 to m. In some cases, only one RF chain may be in RFIC 1002b, or it may be connected to each individual antenna.

[0183] According to an exemplary embodiment of this disclosure, processor 1006b can identify a downlink reference signal from SRS handover resources set by BS 110b. Processor 1006b can use the downlink reference signal to generate downlink channel information and can use previously shared beamcodebook information to select a beam. When no pre-shared beamcodebook exists, processor 1006b can design an optimal beam. Processor 1006b can design a new beam taking into account receive performance and spatial characteristics, and can control beamformer 1004b based on the determined beam.

[0184] The beamformer 1004b according to an exemplary embodiment of this disclosure can be connected to the processor 1006b. Furthermore, the beamformer 1004b can form a beam based on beam information selected (or designed) by the processor 1006b. The formed beam can then be used to transmit an SRS switching signal to the BS 110b.

[0185] According to an embodiment of this disclosure, processor 1006b can select a PMI based on CSI-RS received from BS 110b using a first beam, and can send the selected PMI to the BS. BS 110b can use the final beam to transmit downlink signals including data, and processor 1006b can process the received downlink signals. The final beam can be determined using information obtained from the SRS switching signal and information obtained from the PMI.

[0186] Figure 10C This is a block diagram illustrating the structure of a wireless communication device based on a reinforcement learning method according to an exemplary embodiment of the present disclosure.

[0187] Reference Figure 10C The wireless communication device 100c may include first antennas 1 to m, RFIC 1002c, and processor 1006c. The processor 1006c may include a machine learning device 1010c for performing a reinforcement learning-based antenna selection method, a reinforcement learning-based beam selection method, or a reinforcement learning-based PMI selection method.

[0188] For example, the machine learning device 1010c can observe the state, select an action, and calculate the reward and Q in order to execute... Figure 7A A Q-learning-based antenna selection method. In other words, the machine learning device 1010c can perform... Figures 7A to 7C and Figure 9B The operations used for reinforcement learning are disclosed in the document, and their detailed descriptions will be omitted.

[0189] As an example, in Figure 7AIn the Q-learning-based antenna selection method, the machine learning device 1010c can use the Q table in [Table 3] to calculate Q(S, A) with the maximum value in a given state, and select the antenna combination corresponding to the corresponding Q value based on the learned information.

[0190] Although the inventive concept has been specifically shown and described with reference to its embodiments, it should be understood that various changes in form and detail may be made therein without departing from the spirit and scope of the appended claims and their equivalents.

Claims

1. A method of operating a wireless communication device including a plurality of antennas, the method comprising: Determine an antenna subset that includes at least one of the plurality of antennas; The detection reference signal (SRS) switching signal is transmitted to the base station through at least one antenna of the antenna subset; The channel state information reference signal (CSI-RS) transmitted from the base station is received through the first beam; Select the precoding matrix indicator PMI based on CSI-RS; Send the selected PMI to the base station; as well as Receive signals transmitted from the base station via a second beam determined based on the SRS handover signal and PMI. The method further includes: Monitor the gain value of the second beam; The final antenna subset is determined based on the monitored gain value of the second beam; The final subset of antennas is tracked within each tracking period, wherein the tracking period is determined based on an indicator related to changes in the radio channel; and Based on the tracking results, change at least one antenna included in the final antenna subset.

2. The method according to claim 1, wherein, When the number of SRS handover resources allocated by the base station for the SRS handover signal is less than the number of receiving antennas of the wireless communication device, the step of determining the antenna subset is performed.

3. The method according to claim 1, wherein, When the number of RF chains in a wireless communication device is less than the number of receiving antennas in the wireless communication device, the step of determining the antenna subset is performed.

4. The method according to claim 1, wherein, The monitoring steps include: calculating the gain value of the second beam based on at least one of the power of the received signal, the signal-to-noise ratio (SNR) of the received signal, the frequency efficiency, and the decoding performance of the received signal.

5. The method according to claim 1, wherein, The steps for determining the antenna subsets include: for each transmission cycle of the SRS switching signal, sequentially determining each antenna subset from the multiple antenna subsets.

6. The method according to claim 1, wherein, The steps for determining the final antenna subset based on the gain value of the monitored second beam include: when the gain value of the monitored second beam exceeds a predetermined threshold, the antenna subset is determined as the final antenna subset.

7. The method according to claim 1, wherein, The steps for determining the antenna subsets include: sequentially determining each antenna subset within the plurality of antenna subsets based on the spatial correlation between the plurality of antennas.

8. The method according to claim 1, wherein, The steps for determining the antenna subset include: determining the antenna subset based on reinforcement learning.

9. The method according to claim 1, wherein, The steps for determining an antenna subset include determining the antenna subset based on at least one of the following: the signal-to-interference-plus-noise ratio (SINR) of the wireless communication device, the transmit / receive characteristics of the antenna, and the linearity of the transmit power amplifier.

10. The method according to claim 1, wherein, The steps for selecting a PMI include: selecting a PMI based on information about the weights applied to the CSI-RS receive channel.

11. The method according to claim 1, wherein, The steps for selecting a PMI include: selecting a PMI based on reinforcement learning.

12. A wireless communication device, comprising: Multiple antennas; A radio frequency integrated circuit (RFIC) includes a switching network connected to the plurality of antennas, wherein the switching network is configured to transmit a Sounding Reference Signal (SRS) switching signal to a base station through at least one antenna of a subset of the plurality of antennas; and The processor is configured as follows: Determine the antenna subset; The precoding matrix indicator (PMI) to be provided to the base station is selected based on the Channel State Information Reference Signal (CSI-RS) transmitted from the base station via the first beam; and Processing signals transmitted from the base station via a second beam determined based on SRS handover signals and PMI. The processor is also configured as follows: Monitor the gain value of the second beam; The final antenna subset is determined based on the monitored gain value of the second beam; The final subset of antennas is tracked within each tracking period, wherein the tracking period is determined based on an indicator related to changes in the radio channel; and Based on the tracking results, change at least one antenna included in the final antenna subset.

13. The wireless communication device as claimed in claim 12, wherein, When the number of SRS handover resources allocated by the base station for SRS handover signals is less than the number of receiving antennas of the wireless communication device, the processor is configured to determine a subset of antennas.

14. The wireless communication device as claimed in claim 12, wherein, When the number of RF chains in a wireless communication device is less than the number of receiving antennas in the wireless communication device, the processor is configured to determine a subset of antennas.

15. The wireless communication device as claimed in claim 12, wherein, The processor is configured to sequentially determine each antenna subset from a plurality of antenna subsets for each transmission cycle of the SRS switching signal.

16. A method for operating a base station to communicate with a wireless communication device including a plurality of antennas, the method comprising: Receive a detection reference signal (SRS) switching signal transmitted through an antenna subset including at least one of the plurality of antennas; Estimating uplink channel information based on SRS handover signals; Estimate downlink channel information based on estimated uplink channel information; The first beam is determined and formed based on the estimated downlink channel information, wherein the channel state information reference signal CSI-RS is transmitted through the first beam; Receive the precoding matrix indicator (PMI) from the wireless communication device; A second beam is determined and formed based on the received SRS handover signal and the received PMI, wherein a signal including data is transmitted through the second beam. The gain value of the second beam is monitored by the wireless communication device, and the final antenna subset is determined by the wireless communication device based on the monitored gain value of the second beam. In this process, a final subset of antennas is tracked by a wireless communication device in each tracking period, wherein the tracking period is determined according to an indicator related to changes in the radio channel, and the wireless communication device modifies at least one antenna included in the final subset of antennas based on the tracking results.

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